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CNC self build bass


budget bassist
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Oh, for anyone thinking of doing this, I'll quickly explain how we flipped the slab to machine the other side.

Basically, we drew up a 2D CAD file which was the shape of the outline of the slab at its longest points, and told the router to drill three holes on each long edge, parallel and symmetrical to each other, all the way through the slab and about 10mm into the router bed. We then used 12mm dowels to locate the slab in the bed, and then screwed it down and zeroed to the bottom right corner. The idea being that when we come to flip the wood, the dowels will relocate and the slab will stay square and the router will retain it's zero point.
To complicate things, we had to shift the design 15mm to one side in the slab so as to fit it all on. The easiest way for us to do this was to tell the program to cut the shape in the centre of the block of material, and then shift the router zero point +15mm on the Y axis. This means we then had to shift it -30mm when we flipped it, in order to retain the correct point of reference.

As we were screwing the slab down, it needed to stay in contact with the body so that it doesn't move around when it's nearing completion, so we added "tabs" in the program, just a couple about 20mm wide. This means the finished body will sit inside a frame of material when done, and then I will have to cut it out and sand the tabs flush.
I'm sure there are probably better ways of doing this, but it was the easiest way to do it for us. For example, I've seen someone who cuts the front of the guitar first, then mounts it to a lump of MDF which it's screwed to via a block mounted in the pickup cavity. The MDF locates in some dowel holes that the original block of material was located in, in order to retain X and Y zero. The Z-axis zero is then reset for the new height, and the complete shape is cut. This is something I'd like to experiment with as it would leave totally clean edges.

This all makes much more sense if you look at the above photos by the way!

Edited by budget bassist
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I was wondering how you were intending to keep the body stable as the body was approaching the point of dropping out of the slab (wondered if you were going to use dowels into holes in the bridge area and screws through the neck heel). Looking forward to photos of the next stage.

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Dowels in the bridge area could have been a good idea, I didn't think of that. It would locate the body, but you couldn't secure it that way. The router may pass over any surface of the thing on either side, so I'd rather not risk sticking screws in any of the surfaces it may touch for fear of ruining the bit (and potentially the whole piece of work), even if you get it in nice and deep, i'd rather not risk it. This is why i mentioned screwing it to a bit of MDF from the underside that has already been machined, and then screwing the MDF to the bed, if that makes sense?

I'm aware that some do secure the body through the neck pocket, though I'm not sure I'd like to.

Edited by budget bassist
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Starting the back this morning, photo of it getting started on the roughing pass:

[attachment=172142:IMG_4311.jpg]

I also fitted up the neck and a pickup off the donor guitar (cheapo shine SG copy) a friend lent me to take measurements from etc., fit lovely and snug! Going to do this one for him next I think.

[attachment=172141:IMG_4308.jpg]

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Finished routing the body out today. The jig was a tiny bit out, but it doesn't really matter, just means a little more tidying up to do on the edges. Some of the edges are a little rough, so I'm going to have to do plenty of sanding. I got it home and stuck the donor neck and pickup on there and they fit great, there can't be more than a 0.5mm gap around either of them. Excellent start! I'll probably start sanding etc. on monday.

[attachment=172179:IMG_4313.jpg]

[attachment=172180:IMG_4319.jpg]

I won't be using that pickup by the way, just something I had lying around. I'll be sticking in a SD Basslines. I've got a Keen Electronics 3 band pre to go in as well, just need to get that wired up and working. As for the neck, I think I'll sand that back and oil the whole thing. The black headstock is hideous, and I don't like the plasticky finish. I plan to design and build my own neck at some point in the near future. I'm thinking maple on maple.

Edited by budget bassist
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Just thinking about this, if I were to do this again, I may just use the CNC router to cut the outline, neck pocket, pickup and electronics cavities etc. and then just use a plunge router to cut the radius on the edges, and then just use a spokeshave/orbital sander/whatever to cut the stomach and forearm chamfers. Using the CNC router for the whole thing was a great technical exercise, but it just takes so long, and the edges are still really rough. Perhaps if I were to do something highly contoured it would be worth the time, but for regular slab bodies, it just doesn't seem worth it.

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I did think the lengthy CNC process (with what's available in the Fab Lab) would become an issue, hence my suggestion about reducing the cutting area/time. I think you'd be better using a rasp/surform for the forearm chamfer and belly cut, at least in the initial stages. The roughness you've got might be partly down to the choice of timber (is it swamp ash?) and you'd probably find alder would tear less.

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Yep, swamp ash, a harder wood would probably route a lot cleaner like you say. I think I need to play with the feeds and speeds as well, I'm sure I could speed it up loads.

Anyway, I did a little sanding today, managed to get the top edge from looking like this:

[attachment=172224:IMG_4325.jpg]

To this:

[attachment=172225:IMG_4327.jpg]

Edited by budget bassist
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As an aside, I'm thinking of making some money out of this. Would anybody be interested in purchasing the files for a bass/guitar body of this type (or something else) so that you might go cnc it yourself at a local fablab?

Also, would any of you be interested in buying a body? Potentially custom designed, or as part of a pre-designed range? Available finished or unfinished (I still need to work on the finishes, and eventually necks hopefully.) Prices should be reasonable, as I'll be using cnc. If anybody is seriously interested in commissioning some work, please contact me!

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I'd be interested in buying a body if you can do a P Bass body (exact same size) but with a route for a Dimarzio Model One woofer in the neck, usual P pick up in the middle and reversed P pick up between the pick guard and bridge (so the P pick ups end up in a V shape if you know what i mean like on the picture below)

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Go the front and back of the body sanded down to 320 grit today with the orbital sande,r and sanded the neck down to 220. Going to get some more sand paper so I can do the neck and sides of the body down to 320ish and then it should be ready for staining. Dye still not turned up... Though I did only order on Sunday.

I also started work designing a neck in Solidworks. It still needs work, as you can see.

[attachment=172465:IMG_1034.jpg]

[attachment=172466:IMG_1035.jpg]

[attachment=172467:IMG_1036.jpg]

Edited by budget bassist
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It'll be in two pieces, fretboard and the main part of the neck I think, though I'm a little unsure as to the process I'll use when I'm routing it. I'm thinking I'll route the neck and fretboard separately and then glue them together afterwards. I thought about the skunk strip approach, but I'd like to be able to use a variety of different woods for this eventually, which obviously that doesn't lend itself to.

Edited by budget bassist
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I'm thinking of offering 3D CAD files for sale, for personal use, so that other people can do what I've done, without having to learn the CAD skills to design the body. Either bog standard templates, or I could produce custom ones for a little more. Likely to be in the region of a few tens of pounds. Would anyone be interested? I've been working on a few designs - the ones that can be seen earlier in the thread, a Jazz body, an explorer style body, and a Precision body (still need to get the exact dimensions for control cavities etc.)

[attachment=172899:jazz body.jpg]

[attachment=172900:explorer2.jpg]

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